THE AIM OF THIS RESEARCH IS TO ADDRESS FUNCTIONAL ISSUES IN PROTEIN-NUCLEIC ACID INTERACTIONS, INITIALLY USING A WELL STUDIED LAMBDA CRO-OPERATOR COMPLEX AS OUR MODEL SYSTEM. CRO IS THE SMALLEST REPRESSOR OF KNOWN STRUCTURE. THE THREE-DIMENSIONAL STRUCTURE OF THIS COMPLEX IS KNOWN; HOWEVER, THE RESOLUTION OF THE X-RAY DATA IS INSUFFICIENT TO ELUCIDATE THE SPECIFIC MECHANISM BY WHICH THE PROTEIN BINDS TO THE OPERATOR DNA. 15N NMR EXPERIMENTS WITH THIS COMPLEX WILL SERVE TWO FUNCTIONS. THE RESULTS WILL GIVE NEW STRUCTURAL INFORMATION ON THIS PROTEIN-DNA COMPLEX, AND PROVIDE DATA ON WHICH TO BASE PREDICTIONS FOR OTHER LESS WELL CHARACTERIZED PROTEIN-DNA COMPLEXES. THE SIR HAS SUPPLIED DR. EDWARDS WITH MORE THAN 3 GRAMS OF 2-DEOXY-[7-15N]GUANOSINE PHOSPHORAMIDITE. THESE HAVE BEEN USED IN THE SYNTHESIS OF THE 17 BASE-PAIR CRO OPERATOR SEQUENCE IN WHICH EACH GUANOSINE HAS BEEN INDIVIDUALLY LABELED. THIS IS AN ONGOING PROJECT.